cutting oils

In the suds pump on my mill I use whatever soluble oil is cheapest. Sometimes I use a brush in a tin of paraffin for cast iron even though I was taught to cut it dry. For drilling, generous blobs from a squeezy bottle of Rocol RTD

Depends on usage and whether a diyer or semi pro.

Either way i wouldnt go mister absolutely useless for above basic lathe work, generally ok in limited fashion for milling.
I have a fair few tools that wont work without coolant and also quite a few with through coolant a mister cannot supply or manually get at.

The aim is to keep job and or cutter cool and provide a little lubrication, cutters last longer and should get a better finish. Misters for me dont provide enough cooling, in no time developing steam but far better than running dry.

My main tanks running a bit weak now not long finished off 25ltrs of Castrol about 18 months to two years, need to get some more or an alternative.
Not keen on the synthetic to me it just dont look right opaque water but does a good job. Previously used rooks of Listers, loads of Morris types and many from Smith and Allen the last 8 years. Out of all used there was only one type that stank due to being left a couple of weeks mid summer.
Worth mentioning one small tank usually have to top up through evaportion 1-2 ltrs a day in summer, winter 1 ltr about every two weeks.

If really tight, make your own.
Any oil will do along with a detergent. If had to buy even the cheapest oil it will work out dearer than buying ready mixed delivered to your door - pointless.

If you are buying a soluble cutting fluid, I buy the one that is chlorine free. Mainluy because from time to time I do turn and dril Titanium, either grade 2 or grade 5. On most things I just use the rice bran oil in a spray can. Was using canola oil but it does make a mess on the tools after a while. nasty to clean off too. If I am reaming holes and need a really nice sized hole off the reamer, I then use a mixture with castor oil in it. It will allow a hole to be reamed so close to the reamers size that the reamer becomes hard to pit back into the hole. I don't have a flood coolant system, only a suds botle for when needed.

Neil